To enhance the measurement capabilities most T&M equipment has various scales to meet the demand for a range of signal measurements. If you use a large scale to measure a small signal, many people know it will cause deviation, but cannot explain the reason. Let us see how different scales influence the result.
Some Engineers believe that a large scale can measure a greater range of object signal. This means both small and large signals can be observed by the instrument and for this reason, some of them often choose a large scale to implement the measurement. Some keep the scale at the default position and the measurement results can seem perfectly accurate, but is there problem with the measurement?
ADC Quantification Deviation
The quantification deviation inside the instrument can influence the accuracy of the result. Taking the oscilloscope for example, if it has a 9-bit ADC then there will 29 = 512 valid levels. When it is under 1000V scale (Peak-Peak), considering the input maximum ±1000V to share 512 valid bits. The quantification deviation would reach 2000V / 512 = 3.9V
If using this scale to measure something like 11V, it is obvious that the minimum resolution of single ADC sampling cannot measure a 1V signal change.
Owon have broken this technical difficulty by releasing their XDS series 12 and 14 bit oscilloscopes giving a significant advantage in signal measurement resolution. Using the same case of the 1000V scale the 12bit ADC will give about 0.5V resolution, and the 14 bit ADC will give about 0.125v resolution. As can be seen this is a significant advantage when detailed and accurate measurements are made.
The use of the proper scale to measure a signal is important, if it is not necessary, do not choose a large scale to measure small signals. Instead choose a scale that more closely matches the signal levels being measured to ensure accurate results. The OWON XDS oscilloscope range offers user more options to select the most suitable scale, and is designed to help you make more accurate measurements easily.